Potential subjects will be identified in the Emergency Departments (EDs) of two level I trauma centers, located within a few blocks of each other in Houston, Texas. Once discharged from the ED, subjects will be enrolled and baseline procedures will be performed, including behavioral/cognitive testing, sample collection, and medication teaching, including the first dose of study drug. Subjects will be followed by phone at Day 3-4 during the 7-day dosing period of the drug trial, then with return visits for all subjects at one week, one month, three months, and six months after injury.